We seek to develop a technique to treat breast cancer tumors in a minimally invasive way. The tumors would be eradicated using laser energy to photocoagulate the lesion through an incisionless interstitial approach. This approach will be enhanced by the capabilities of a high resolution X-ray, stereotactically guided, system that can accurately locate the lesion in 3 dimensions and deliver a trocar/cannulae to that exact location. After delivery of a specially designed laser energy transparent cannulae to the treatment site, laser energy will be uniformly diffused to treat the lesion with hyperthermia/coagulation. Laser probes will be miniaturized to minimize insertion trauma. This is a technologic approach to concern facing the 184,000 U.S. women yearly, with breast cancer, who live in dread of disfigurement from mastectomy and lumpectomy. We propose to: design, build and test a laser energy diffusing system capable of being stereotactically delivered to safely deliver the energy needed to coagulate clinically relevant tumors, examine the feasibility of monitoring the extent of the coagulated volume with the high resolution X-ray system already in use, and test the combined systems in an ex-vivo- and in-vivo model. PROPOSED COMMERCIAL APPLICATION The focus on the issue of breast cancer, from the mammogram to the possibility of mastectomy or lumpectomy, is one of today's highest health care concerns. A system that could locate and simultaneously treat breast cancer tumors in a minimally invasive way would have huge commercial application.